August 8, 2005

Gene Study Shows Sabertooths Were No Pussy Cats

WASHINGTON -- DNA taken from the teeth of ancient sabertooth cats showed the distinctive-looking animals were cousins of modern-day cats but not direct ancestors, scientists said on Monday.

And they also shot down a theory that cheetahs may have originally evolved from a similar-looking North American ancestor.

"Our results show that the sabertooths diverge early and are not closely related to any living cats," Ross Barnett of the Henry Wellcome Ancient Biomolecules Center in Oxford, Britain and colleagues wrote in their report, published in the journal Current Biology.

Sabertoothed cats went extinct about 13,000 years ago, as did many other large cats that once roamed the North American plains, such as the Yukon scimitartoothed cat, the American lion-like cat or Panthera atrox and a cheetah-like cat called Miracinonyx trumani.

The only large cats that survived in the Western Hemisphere were the puma, also commonly known as a mountain lion or cougar, and the jaguar.

Scientists often classify animals based on bone structure, but genetics allows DNA analysis to more accurately draw family trees.

SEPARATE FAMILY

Sabertooths have been placed in a separate family -- Machairodontinae -- from modern cats such as lions and tigers.

Barnett and a team of researchers from Britain, the United States, Sweden, and Australia managed to get some DNA from a sabertooth's bones, a bit from a related Yukon scimitartoothed cat and a sample from Miracinonyx bones found in Wyoming.

Their analysis shows that the sabertooth cats diverged early on from the ancestors of modern cats and are not closely related to any living feline species.

And the cat that resembled an early cheetah was not in fact a cheetah but a relative of the modern-day puma.

"Despite its remarkable morphological similarity to the African cheetah (Acinonyx jubatus), Miracinonyx appears to have evolved from a puma-like ancestor, presumably in response to similar ecological pressures," the researchers wrote.

In other words, it chased antelope on the rolling plains of the Midwest just as modern cheetahs do in the African savannah.

"It has been suggested that the cheetahs originated in the New World and later migrated to the Old World," the researchers wrote.

"However, the mitochondrial sequence analysis together with recent fossil data suggests that they originated in the Old World and that a puma-like cat then invaded North America around six million years ago," the researchers wrote.

"Around 3.2 million years ago, this ancestor diverged into Miracinonyx and Puma, which is broadly contemporaneous with increasing prairie in North America."